This is a 200 micron Eaton SENTINEL filter bag, size 01. Made of polyester felt with a polypropylene ring, this bag has a description of: PE-200-P01E-WW-50. The last number stands for the number of bags that come per box (50). Box quantities are required when ordering any Eaton filter bags. There are a few unique features of SENTINEL bags. For one, they are entirely welded, not sewn. They also have a special sealing ring that snaps into place in the filter housing and prevents bypass. All felt used is silicone-free and the edges are heat sealed to remove loose fibers.